While not long range I thought I would ask for help here.

I have just developed a repeatable hunting load for my custom 250-3000. 100 gain Sierra SBT at approx 2,800 fps. (I shot my chronograph some time ago ...)

Flags showed a very slight wind from behind me, but I couldn't feel it on my skin.
It is zero'd 0.75" high at 100 yards, dead on vertical.
My 200 yards POI is 2.5" low (expected) but 2.5" to the right with some slight vertical stringing. (warm barrel ? breathing ?)

Is my scope canted ?
If so, which way to correct it ?
Any other ideas ?

My guess would be a slight breeze. A 100gr 25cal bullet has a pretty low BC and it won't take much wind to move it. Spin drift would push it to the right out of a right hand twist barrel, but that effect is pretty small at only 200 yards. Cant could be a contributing factor, but again this is pretty small at only 200. You could try intentionally tilting the rifle to the left to see what the effect is.

Well I returned to the range and with nil detectable wind, I shot a three shot group at 200 yards. This time I tilted the rifle to the left at about 20 deg. ie the scope bore was to the left of the rifle bore. The group went dead centre and as expected, low.

Which way do I rotate the scope to try and eliminate this ?

Set up a target and draw a long line with a spirit level or plumb line and zero so that you are all along that line, dialling up and down. That way you will know that the scope is set up straight.

Going from memory, I think as you found, canting left makes you POI move left. If this is what you want twist the scope to make you naturally want to cant left. In other words twist the scope clockwise if you are behind the rifle. That way you will twist counterclockwise to get an upright scope image when shooting the rifle.

I sugest you mark the rings and scope tube with a pencil, or stick masking tape and mark on that so that you have a reference point for how much you twisted the scope and can easily get a sense as to less or more as required.

Please let us know how it works out. I'm going from memory here, hope I'm not sending you the wrong way, but it seems to line up with your testing.

quote:

Originally posted by Code4:
While not long range I thought I would ask for help here.

I have just developed a repeatable hunting load for my custom 250-3000. 100 gain Sierra SBT at approx 2,800 fps. (I shot my chronograph some time ago ...)

Flags showed a very slight wind from behind me, but I couldn't feel it on my skin.
It is zero'd 0.75" high at 100 yards, dead on vertical.
My 200 yards POI is 2.5" low (expected) but 2.5" to the right with some slight vertical stringing. (warm barrel ? breathing ?)

Is my scope canted ?
If so, which way to correct it ?
Any other ideas ?

1) Could be scope's vertical crosshair doesn't disect the bore correctly

2) or it could be that your unknowingly canting the rifle when you shoot it.

3) or could be the wind - But 2.5" right at 200 yds with nothing showing at 100 would be very unlikely with that light wind you described.

I would tend to agree with Ray. Have you tried this: place your rifle on the bags and then stand back, behind and above the rifle, and look at the alignment of scope and rifle
barrel. Might be too small to see, but worth a try. Also, are the bullet holes at 200 yards round and uniform or elongated?
Peter.

When I get home from fi fo I'll set up the rifle and have a look. Impact holes are nice and round.

I'm starting to think the scope bases may not be aligned with the action - bore or the barrel has been threaded off centre.